Well, I spoke too soon again. I have one-way connection. The wired computer was able to access the wireless one. So I can do my copy and pasting through the wired computer. I'm not going to keep wrestling with it to get the functionality in both directions. Consider it solved for now...
OK, update. I got part of this wrong. There was a mass of wires, so I hadn't checked, but I actually had the wired computer connected to the Netgear router, in turn wired to Xfinity. So I wired that laptop directly to the Xfinity router. Now I can see the shared folders from the other...
I have an XFINITY modem/router with wired connection to one laptop. There is also a Netgear router connected to the XFINITY router that connects various other things around the house.
But for internet, I'm using the 2.4GHz and 5GHz connections from the XFINITY router.
I have a second laptop...